Algae are a diverse group of simple, plant like organisms. Like plants, most algae use the energy of sunlight to make their own food, a process called photosynthesis. However, algae lack the roots, leaves, and other structures typical of true plants. Algae are the most important photosynthesising organisms on Earth. They capture more of the sun’s energy and produce more oxygen (a by-product of photosynthesis) than all plants combined. Algae vary greatly in size and grow in many diverse habitats. Microscopic algae, called phytoplankton, float or swim in lakes and oceans. Although most algae grow in fresh water or seawater, they also grow on soil, trees, and animals, and even under or inside porous rocks, such as sandstone and limestone.
Algae also form mutually beneficial partnerships with other organisms notably with fungi to form lichens-plant-like or branching growths that form on boulders, cliffs, and tree trunks.
The algae provide oxygen and complex nutrients to their partner, and in return they receive protection and simple nutrients. This arrangement enables both partners to survive in conditions that they could not endure alone.
There are more than 15,000 kinds of lichen in the world. They can grow on any surfaces and anywhere in the world. The lichen is a symbiotic association between a fungus (mycobiont) and an alga (photobiont). The filaments of the fungus support cells of the algae.
The fungus needs carbon and energy. Generally it finds it on dead organic material or on living organisms (parasitism) which cause disease to plants. The algae, capable of photosynthesis, provide the carbohydrates it needs. It also provides some vitamins (biotin, thiamine). The algae changes the structure of the fungus which can absorb a lot of water and a part of sunlight to protect the algae from certain strong wavelengths.
The fungal component of lichens produces organic acids that disintegrate rock, giving the lichen a better hold and contributing to the weathering process, which eventually turns a rock into soil. Lichens can withstand great extremes of temperature and are found in all parts of the world. In the built environment, the organic acids are notoriously deleterious to zinc and lead used for flashing or gutter lining.
Many small plants bearing the name moss are not mosses in that they do not belong to the Bryophyta family. The “moss” found on the north side of trees is the green alga Pleurococcus;
Irish moss is a red alga. Beard lichen (beard moss), Iceland moss, oak moss, and reindeer moss are lichens. Spanish moss is also a term used for a lichen. The term moss used in connection with MossGo does not refer to Bryophytas, but to the vernacular use of the word.